[python package] function get_leaf_output bugfixed (#717)
[python package] function get_leaf_output bugfixed (#717)

missing parameter "self" in signature of Booster.get_leaf_output
Allardvm/LightGBM,wxchan/LightGBM,huanzhang12/LightGBM,wxchan/LightGBM,Laurae2/LightGBM,henry0312/LightGBM,Allardvm/LightGBM,olofer/LightGBM,Allardvm/LightGBM,olofer/LightGBM,Laurae2/LightGBM,huanzhang12/LightGBM,wxchan/LightGBM,Laurae2/LightGBM,microsoft/LightGBM,henry0312/LightGBM,olofer/LightGBM,henry0312/LightGBM,wxchan/LightGBM,Allardvm/LightGBM,olofer/LightGBM,Laurae2/LightGBM,microsoft/LightGBM,huanzhang12/LightGBM,microsoft/LightGBM,henry0312/LightGBM,wxchan/LightGBM,henry0312/LightGBM,huanzhang12/LightGBM,microsoft/LightGBM,huanzhang12/LightGBM,Allardvm/LightGBM,olofer/LightGBM,Laurae2/LightGBM,microsoft/LightGBM